n = int(input())
s = input()

count = 0

for pi1 in range(len(s) - 4):
  for pi2 in range(pi1 + 1, len(s) - 3):
    for pi3 in range(pi2 + 1, len(s) - 2):
      for pi4 in range(pi3 + 1, len(s) - 1):
        for pi5 in range(pi4 + 1, len(s)):
          p1 = s[pi1]
          p2 = s[pi2]
          p3 = s[pi3]
          p4 = s[pi4]
          p5 = s[pi5]
          flag = p1 == p3
          flag = flag and p1 != p2
          flag = flag and p1 != p4
          flag = flag and p1 != p5
          flag = flag and p2 != p4
          flag = flag and p2 != p5
          flag = flag and p4 != p5
          if flag:
            count += 1
print(count)